Structure elucidation of the algal carotenoid (3S,5R,6R,3'S,5'R,6'S)-13'-cis-7',8'-dihydroneoxanthin-20'-AL 3'-beta-lactoside (P457). Part 2, Nmr studies.

Extensive nmr studies on the algal carotenoid P457 [1], its octaacetate 2, and a heptaacetate 3 resulted in the elucidation of its structure including the C-13'-cis configuration of the cross-conjugated C-20'-al chromophore, the relative stereochemistry of the allenic end group, the presence of an uncommon C-7',C-8'-single bond, the C-5',C-6'-epoxide, and of a beta-lactoside attached to C-3' of the carotenoid. P457 [1] is one of the most structurally complex carotenoids known, and its 1H- and 13C-nmr data have been fully interpreted.